John cant satisfy Lydia and they need your help

John seems unsure on how to begin or what to say until Lydia sighs a bit impatiently. "Just tell him"
"Alright.", John begins, then hesitates again. "I can trust you right?"
"Of course you can" you say. Whatever it was, it really seems to bother John. You cant help but notice Lydia staring at your bare torso. For a second you think about quickly grabing a shirt, but that doesnt feel any less weird now.
"You can tell no one about this", John says, seemingly to convince himself as well to finally get it out.
"Of course not.", you answer, trying to hide your slight impatience.
"Alright, so...Lydia and I talked about this. and we love each other, but we dont think theres another way except this and thought maybe you...well...you could..."
John hesitates, but Lydia interrupts. "John cant keep me satisfied in bed."
You blink, surprised, you didnt expect the conversation to turn this direction. You look at John, half expecting him to deny it, but he just nods, avoiding your gaze.

Since he doesnt say anything, Lydia continues, clearly getting more into it while she speaks. "To be completely honest, his little dick neither lasts long nor does it feel good, thats why I already have these.", and she points to two small keys hanging around the chain she wears. You suspect it. "Are these the keys for..."
"His chastity cage, yeah. I though if he wasnt distracted by himself, he could at least satisfy me with like, a strap-on or something, but its just not the same. So we came to you." She smiles at you again. Fuck shes hot.
John nods and looks at you. "You remember how I came into your room and accidentaly caught you jerking off one time?"
You try not to blush, its not one of your fondest memories, but you do remember. John continues. "Well I saw your penis and it looked...well...definetly bigger than mine, and I can sometimes hear through the walll how your guests feel overnight."
Slightly embarrassed, you think about the fact that thin walls have never been a concern for you, and what John, but also Emily must have overheard over the months.

"And then we thought", John continues, "Just if you´re okay with it, we could maybe try, you know...if that works."

After a short pause, you slowly say: "So to be clear...you want me to sleep with your girlfriend?"
"If it goes well, yes."

You look at Lydia, who nods. While she tries to look serious, you can see the hint of a smile in her expression.

"Alright", you say, still wondering if this is some kind of confusing prank, "When, and how, do you want to try this?"